THE VASC^ULAR DRAINAGE OF THE ENDOLYM- 

 PHATIC SAC AND ITS TOPOGRAPHICAL RELA- 

 TION TO THE TRANSVERSE SINUS IN THE HUMAN 

 EMBRYO 



GEORGE L. STREETER 



Department of Embryology, Carnegie Institution of Washington 



SIX FIGURES 



CONTENTS 



Introduction 67 



Material and methods 08 



Historical 69 



Endolymphatic appendage at different stages 



1. Human embryos one and two months old 73 



2. Hmnan embryos during third month 77 



3. Human embryos four months old 81 



4. Human embryos during seventh month 85 



Summary ! 87 



References cited .' 89 



INTRODUCTION 



In a previous paper (Streeter '14) dealing with some experi- 

 mental studies on amphibian larvae, it was shown that in the 

 tadpole the endolymphatic sac always lies in close apposition to 

 the membranous roof of the hind-brain. This relation exists not 

 only in normal specimens, but it was also found that in specimens 

 where the ear vesicle had been rotated or transplanted by opera- 

 tive procedure, the endolymphatic sac in the subsequent self- 

 correction of posture, succeeds in most cases in attaching itself 

 to the membranous chorioidal roof in the normal manner. 



This interesting topographical relation of the endolymphatic 

 sac in the tadpole, induced the writer to examine more closely the 

 endolymphatic sac in later human embryos, and it is the purpose 

 of the present paper to outline the results of such a study in 

 embryos from 20 mm. to 240 mm. crown-rump length. 



67 



